Bulletin of the American Physical Society
Fall 2011 Meeting of the APS Prairie Section
Volume 56, Number 13
Thursday–Saturday, November 10–12, 2011; Cedar Falls, Iowa
Session C1: Astrophysics and Cosmology |
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Chair: Michael Roth, University of Northern Iowa Room: UNI Center for Enery and Environmental Education Auditorium |
Friday, November 11, 2011 8:00AM - 8:50AM |
C1.00001: Seeing through the dust: Unveiling massive star formation with ALMA Invited Speaker: Charles Kerton Compared to stars like our Sun massive stars are relatively rare, evolve more rapidly, and form in more highly obscured environments. The result is that our understanding of massive star formation is at a much more rudimentary state compared with our view of how lower mass stars form. Transforming our understanding of this process is just one of the science goals of the Atacama Large Millimeter Array (ALMA). This new international radio observatory has just started early science observations and will be used for astrophysical studies ranging from the exploration of the dark ages of our Universe's history to mapping plumes from volcanic eruptions on Io. This talk will focus how astrophysicists plan to use the unique capabilities of ALMA to explore the birthplaces of massive stars in our Galaxy. [Preview Abstract] |
Friday, November 11, 2011 8:50AM - 9:02AM |
C1.00002: Special Relativistic effects may impact the conditions necessary for an event horizon John Laubenstein The predictions of General Relativity (GR) have been well tested, yet the precision needed to differentiate GR from other potential theories lies well beyond the level of precision available through current (and even proposed) experimentation. As such, any effort to differentiate theories must go beyond observation and be based on exact mathematical relationships. This paper explores the derivation of the Schwarzschild metric with a particular focus on the value of the metric in weak gravity where GR reduces to Newtonian gravity. Specifically, this paper explores the ramifications of including Special Relativistic (SR) effects into the weak field approximation used to derive the value of the parameter $\frac{1}{S}$ in the Schwarzschild metric expressed as: $ds^2=\left( {1+\frac{1}{Sr}} \right)^{-1}dr^2+r^2\left( {d\theta ^2+\sin ^2\theta d\phi ^2} \right)+K\left( {1+\frac{1}{Sr}} \right)dt^2$ . It can be shown that when SR effects are fully taken into account, including when v $<< \quad c$, that the conditions necessary to support the formation of the event horizon change. This paper explores whether these changes are significant enough to call into question the predictions of GR or whether they may be legitimately ignored as has been the past practice. [Preview Abstract] |
Friday, November 11, 2011 9:02AM - 9:14AM |
C1.00003: Infrared Observations of Massive Star Forming Regions Sarah Willis, Massimo Marengo, Lori Allen, Giovanni Fazio, John Bally, Leo Bronfman, Sean Carey, Luis Chavarria, Rob Gutermuth, Tom Megeath, Ron Probst, Guy Stringfellow We have observed NGC 6334 with NASA's Spitzer Space Telescope, using the IRAC infrared imager at wavelengths of 3.6 - 8.0 microns, and NEWFIRM, a ground based near-infrared imager at wavelengths of 1.1 - 2.4 microns. NGC 6334 is a giant molecular cloud with a complex history of star formation located approximately 1.6 kpc away in the plane of the Milky Way Galaxy. NGC 6334's high cloud mass ($>$10$^{5}$ M$_{o}$) and bright far-infrared luminosity identify it as a local analog to the unresolved sites of star formation found in other galaxies. Observing high mass Galactic regions such as NGC 6334 will provide the missing link necessary to match empirical relations between the efficiency / rate of star formation and the global properties of the molecular cloud derived from nearby, lower mass star forming regions to results from external galaxies. Our preliminary results reveal that NGC 6334 contains several hundred Class I YSOs and several thousand Class II (older) YSOs concentrated at multiple sites of star formation across the molecular cloud complex. [Preview Abstract] |
Friday, November 11, 2011 9:14AM - 9:26AM |
C1.00004: Mid-Infrared Substellar Companion Mass Limits for Nearby Planet-Host Stars Alan Hulsebus, Massimo Marengo, Karl Stapelfeldt, Joe Carson The sensitivity of the Infrared Array Camera on NASA's Spitzer Space Telescope at 4.5 $\mu$m provides the ability to use direct imaging to capture light from brown dwarfs expected to have peak emission in this band. Using PSF subtraction techniques, we can detect sources with better than 10$^{4}$ contrast at separations as close as 12 arcseconds. Potential substellar companions can be identified from their characteristically red colors between the 3.6 and 4.5 $\mu$m photometric bands. In a sample of 14 nearby stars already found to have planetary companions from radial velocity searches, we found no sources consistent with substellar-mass companion colors within 20 arcseconds of the stars. This corresponds to 4.5 $\mu$m upper limits for objects of 5 Jupiter masses at 1 Gyr age and 10 pc distance. I will present a description of the point spread function and artifact subtraction process necessary to achieve this result. [Preview Abstract] |
Friday, November 11, 2011 9:26AM - 9:38AM |
C1.00005: Cosmic Ray Induced Neutron Irradiation Andrew Overholt After cancer studies performed on flight crews during the 1970s, it was found that cosmic rays produce a signficant flux of thermal neutrons at airplane altitudes. In the case of high energy cosmic rays these biologically threatening neutrons are increased at ground level. Our work models the flux of neutrons produced by high energy cosmic rays, exploring the possibility of biological impact due to extended periods of increase high energy cosmic ray flux. [Preview Abstract] |
Friday, November 11, 2011 9:38AM - 9:50AM |
C1.00006: Consequences of intense intermittent astrophysical radiation sources for terrestrial planets Adrian Melott Life on Earth has developed in the context of cosmic radiation backgrounds. This in turn can be a base for comparison with other potential life-bearing planets. Many kinds of strong radiation bursts are possible by astrophysical entities ranging from gamma-ray bursts at cosmological distances to the Sun itself. Many of these present potential hazards to the biosphere: on timescales long compared with human history, the probability of an event intense enough to disrupt life on the land surface or in the oceans becomes large. One of the mechanisms which comes into play even at moderate intensities is the ionization of the Earth's atmosphere, which leads through chemical changes (specifically, depletion of stratospheric ozone) to increased ultraviolet-B flux from the Sun reaching the surface. UVB is extremely hazardous to most life due to its strong absorption by the genetic material DNA and subsequent breaking of chemical bonds. We characterize intensities at the Earth and rates or upper limits on rates. We estimate how often a major extinction-level event is probable given the current state of knowledge. Moderate level events are dominated by the Sun, but the far more severe infrequent events are dominated by gamma-ray bursts and supernovae. So-called ``short-hard'' gamma-ray bursts are a substantial threat, comparable in magnitude to supernovae and greater than that of the higher-luminosity long bursts considered in most past work. Short bursts may come with little or no warning. [Preview Abstract] |
Friday, November 11, 2011 9:50AM - 10:02AM |
C1.00007: Galactic Arms of Spiral Galaxies Originated From External Orbits Stewart Brekke Due to the Big Bang galactic arms were orbiting each other in sets of two or more. As the orbits decayed due to gravitational attraction, they tangentially collided and attached in their fore-sections forming spiral galaxies which began rotating transforming the orbital motion of the pre- galactic arms into rotational motion of the newly formed spiral galaxy. One can observe that the galactic arms originated from external orbits in the existing galaxies such as M51, M99, M83, M101, NGc 1232 and NGC 1365 among many others in the universe. [Preview Abstract] |
Friday, November 11, 2011 10:02AM - 10:14AM |
C1.00008: Direct detection of dark matter with the DarkSide experiment Andrew Alton, Erika Zetterlund The DarkSide collaboration has constructed and operated a 10 kg prototype argon time projection chamber. We are designing a 50 kg model that will work as a first physics detector and also serve as a prototype for a ton sized detector. We will present an overview of the detector and what design features make it unusual. Monte Carlo simulations will be shown and preliminary data will be presented. [Preview Abstract] |
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